I have had an issue lately where when im stopped the rpms get irratic. It dosen't happen every time I drive it but I have noticed it happening more frequently. I just switched to a 60 percent biodiesel blend and now the problem is way worse. It will idle OK for a while and then get very irratic to the point where it wants to die. It sounds like the eninge is starving for fuel. I changed the fuel filters and it had no effect. I have and edge insight and the FICM voltage, battery voltage is fine. I have around 49 volts on the FICM. A friend of mine told me it is probably my fuel pump. He and another guy had a similar issue on their 6.0's around the same miles and changing the fuel pump fixed the problem. He also runs biodiesel and said since it is thicker it may have made the fuel pump issue more pronounced since it has to work harder now. I do not have a fuel pressure gauge. I have 75000 miles on it right now. The biodiesel reaction was perfect, passes the 27/3 test, washed 4 times until the wash water was clear, and completly de watered. Any ideas would be appreciated.